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Historically, roof pitch was designated in two other ways: A ratio of the ridge height to the width of the building (span) [6] and as a ratio of the rafter length to the width of the building. [7] Commonly used roof pitches were given names such as: Greek: the ridge height is 1 ⁄ 9 to 1 ⁄ 7 the span (an angle of 12.5° to 16°);
Among its basic uses are marking common, hip, valley and hip, or valley jack rafters, laying out stair stringers, determining and marking angles, and making square cuts on boards. Common lines made using a speed square include perpendicular cut marks and Angles definition of an angle for roofs, stairways, and decks. The tool uses a 0° reference.
The "hips" and hip rafters sit on an external corner of the building and rise to the ridge. Where the building has an internal corner, a valley makes the join between the sloping surfaces (and is underlain by a valley rafter). Hip roofs have the advantage of giving a compact, solid appearance to a structure. The roof pitch (slope) may vary.
The hip or valley rafter also connects the ridge to the plate, but lies at a 45-degree angle to the common rafter. This number gives the length of the hip or valley rafter per seventeen units of run. Difference in lengths jacks. The jack rafters lie in the same plane as the common rafter but connect the top plate (the wall) or ridge board to ...
Compass rafter: A rafter curved or bowed on the top (the top surface of a rafter is called its "back") or both the top and bottom surfaces. Curb rafter: The upper rafters in a curb (kerb, gambrel, Mansard roof) roof. Hip rafter (angle rafter): The rafter in the corners of a hip roof. The foot of a hip rafter lands on a dragon beam.
Key:1: ridge beam, 2: purlins, 3: common rafters. This is an example of a "double roof" with principal rafters and common rafters. A timber roof truss is a structural framework of timbers designed to bridge the space above a room and to provide support for a roof.
[5] [6] The term truss has often been used to describe any assembly of members such as a cruck frame [7] [8] or a couple of rafters. [ 9 ] [ 10 ] One engineering definition is: "A truss is a single plane framework of individual structural member [sic] connected at their ends of forms a series of triangle [sic] to span a large distance".
A hammer-beam is a form of timber roof truss, allowing a hammerbeam roof to span greater than the length of any individual piece of timber.In place of a normal tie beam spanning the entire width of the roof, short beams – the hammer beams – are supported by curved braces from the wall, and hammer posts or arch-braces are built on top to support the rafters and typically a collar beam.